Project 2 has two main goals. One is to develop animal models for investigating how specific B. pseudomallei virulence factors contribute to the establishment and course of respiratory infection, the induction of inflammation and innate immunity, and the development of adaptive and potentially protective immunity. These models will be used to evaluate the in vivo functions of the B. pseudomallei virulence factors and regulatory systems identified in Projects 1 and 3, to assess the contribution of specific host defense mechanisms using gene knock-out mice as described in Project 4, and to test potential component vaccine candidates identified in Projects 1, 2 and 3. These models therefore represent an essential core resource for this program project. The second goal of Project 2 is to determine if a specific B. pseudomallei gene with the potential to encode a filamentous hemagglutinin (FHA)-like protein does in fact represent a bona fide Burkholderia virulence gene. FHA is a multifunctional virulence factor expressed by Bordetetta pertussis that represents a major adhesin and an important immunoprotective component of newly formulated acellular pertussis vaccines. Dr. Peggy Cotter, Project 2 leader and program PI, has been studying Bordetella pathogenesis since 1992. Her contributions include the development of several natural-host animal models for studying B. bronchiseptica, the evolutionary progenitor of B. pertussis', the discovery that the BvgAS master virulence regulatory system controls multiple and distinct phenotypic states, each with unique and important roles in the infectious cycle; and extensive analyses of the relative roles of fimbriae (pili) and FHA in Bordetella-host interactions. Dr. Cotter's expertise in the development of genetic systems to manipulate pathogen genomes and the development of animal models to study infection are essential components of this program.